Analyzing the Ability of Astragalus tennesseensis to Accumulate Selenium

Abstract

Selenium (Se) is a naturally occurring essential micronutrient that can be accumulated by some plants. When accumulated above 1,000 μg Se per gram of plant dry weight (μg/g), the plant is labeled as a Se hyperaccumulator (Alford et al., 2012). Astragalus bisulcatus is one of the most well-studied Se hyperaccumulators. Astragalus tennesseensis is a related species, but there is currently no literature observing its ability to accumulate Se. This project investigated whether A. tennesseensis can accumulate Se. Both species were grown in a greenhouse to compare the amount of Se each would accumulate. Sodium selenate (Na2SeO4) was applied to test groups weekly at 1 μg Se per gram of soil for eight weeks. After treatment was completed, each plant was separated into above and below-ground parts to be dried and digested in nitric acid to analyze Se content. Samples were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) to determine the Se content. The average Se content in dosed A. bisulcatus shoots (219 μg/g), was not found to differ from A. tennesseensis shoots (205 μg/g), although the Se content was expected to be much higher in A. bisulcatus (above 1,000 μg/g) due to its status as a known hyperaccumulator. However, when compared to control groups (avg 1.72 μg/g in A. bisulcatus shoots, avg 1.46 μg/g in A. tennesseensis shoots), both species in test groups had much higher levels of Se. Therefore, it can be concluded that Se treatment did indeed increase levels of Se in both species, and that A. tennesseensis has the ability to accumulate Se from soil. Nonetheless, due to the unexpectedly low values in A. bisulcatus, it was not possible to determine if A. tennesseensis could be classified as a Se hyperaccumulator.